The green synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives catalyzed by acidic ionic liquid under ultrasound irradiation

Abstract-A novel and efficient method has been developed for the synthesis of pyrano[3,2-c]quinoline-2,5-dione derivatives by the convenient ultrasound-mediated condensation of 4-hydroxyquinolin-2-one with Meldrum’s acid and aldehydes in the presence of a catalytic amount of [HMIm]HSO4 as a green, efficient and reusable acidic ionic liquid medium. The stability of the ionic liquid during the reaction was high and, used for several times to recycled form. Placing the reaction mixture under ultrasound condition causes that we have lower energy consumption and achieve to the desired product in the optimal time. The method is simple, starts from readily accessible commercial starting materials, and provides biologically interesting products in good yields and short reaction times.